极客笔记在Python的Pandas中向现有的DataFrame中添加新列
在本教程中，我们将学习如何向现有的DataFrame中添加新列。我们可以使用不同的方法来添加新列。让我们来看看所有方法。
使用列表
我们可以使用列表来添加新列。按照以下步骤来添加新列。
算法
1. Create DataFrame using a dictionary.
2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame.
3. Add the list to the DataFrame like dictionary element.
让我们看一个例子。
例子
# importing pandas
import pandas as pd
# creating a DataFrame
data = {
'Name': ['Hafeez', 'Aslan', 'Kareem'],
'Age': [19, 18, 15],
'Profession': ['Pythoneer', 'Programmer', 'Student']
}
dataframe = pd.DataFrame(data)
print('-----------Before adding a new column----------')
print(dataframe)
print('\n\n')
# creating a list for new column
places = ['Nellore', 'Mumbai', 'Andhra']
# we are using 'Places' as column name
# adding the list to the dataframe as column
dataframe['Places'] = places
print('---------------After adding a new column------------')
print(dataframe)
输出结果
如果你运行上面的程序，你将得到以下结果。
-----------Before adding a new column----------
Name Age Profession
0 Hafeez 19 Pythoneer
1 Aslan 18 Programmer
2 Kareem 15 Student
---------------After adding a new column------------
Name Age Profession Places
0 Hafeez 19 Pythoneer Nellore
1 Aslan 18 Programmer Mumbai
2 K areem 15 Student Andhra
DataFrame.insert()
有一个内置的方法叫做 insert() 用于添加新的列。按照以下步骤操作。
算法
1. Create DataFrame using dictionary.
2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame.
3. Insert the data into the DataFrame using DataFrame.insert(index, column_name, data)
method.
示例
# importing pandas
import pandas as pd
# creating a DataFrame
data = {
'Name': ['Hafeez', 'Aslan', 'Kareem'],
'Age': [19, 18, 15],
'Profession': ['Pythoneer', 'Programmer', 'Student']
}
dataframe = pd.DataFrame(data)
print('-----------Before adding a new column----------')
print(dataframe)
print('\n\n')
# creating a list for new column
places = ['Nellore', 'Mumbai', 'Andhra']
# we are using 'Places' as column name
# adding the list to the dataframe as column using insert(index, column_name, data)
dataframe.insert(2, 'Places', places)
print('---------------After adding a new column------------')
print(dataframe)
输出
如果你运行上述程序，你将得到以下结果。
-----------Before adding a new column----------
Name Age Profession
0 Hafeez 19 Pythoneer
1 Aslan 18 Programmer
2 Kareem 15 Student
---------------After adding a new column------------
Name Age Places Profession
0 Hafeez 19 Nellore Pythoneer
1 Aslan 18 Mumbai Programmer
2 Kareem 15 Andhra Student
DataFrame.assign()
该方法接受一个参数，即数据的列表，并将其作为列添加到数据框的末尾。
算法
1. Create DataFrame using a dictionary.
2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame.
3. Insert the data into the DataFrame using DataFrame.assign(column_name = data)
method. It returns a new data frame. So, we have to store it.
4. Print the new data frame.
让我们来看一个例子。
例子
# importing pandas
import pandas as pd
# creating a DataFrame
data = {
'Name': ['Hafeez', 'Aslan', 'Kareem'],
'Age': [19, 18, 15],
'Profession': ['Pythoneer', 'Programmer', 'Student']
}
dataframe = pd.DataFrame(data)
print('-----------Before adding a new column----------')
print(dataframe)
print('\n\n')
# creating a list for new column
places = ['Nellore', 'Mumbai', 'Andhra']
# we are using 'Places' as column name
# adding the list to the dataframe as column using assign(column_name = data)
new_dataframe = dataframe.assign(Places = places)
print('---------------After adding a new column------------')
print(new_dataframe)
输出
如果你运行上述程序，你将得到以下结果。
-----------Before adding a new column----------
Name Age Profession
0 Hafeez 19 Pythoneer
1 Aslan 18 Programmer
2 Kareem 15 Student
---------------After adding a new column------------
Name Age Profession Places
0 Hafeez 19 Pythoneer Nellore
1 Aslan 18 Programmer Mumbai
2 Kareem 15 Student Andhra
结论
如果您对教程有任何疑问，请在评论部分提及。